In some cases, an external magnetic “bone conduction hearing device” (“BCHD”) is held in position on a patient's head by means of magnetic coupling that occurs between one or more magnetic members included in a baseplate or spacer of the BCHD and a magnetic implant that has been implanted beneath the patient's skin and affixed to the patient's skull. Acoustic signals originating from a transducer located in the external magnetic BCHD are transmitted through the baseplate or spacer (which is coupled to the transducer of the BCHD) and through the patient's skin to bone in the vicinity of the underlying magnetic implant, and then through the skull bone to the patient's cochlea. The acoustic signals generated and delivered by the transducer to the baseplate or spacer are provided in response to external ambient audio signals detected by one or more microphones disposed in external portions of the hearing aid, which are processed by a processor in the BCHD and provided to the transducer. The transmission of acoustic signals from the BCHD to the patient's bone occurs through skin and other tissue overlying the bone, and may also be through hair disposed between the baseplate or spacer and the magnetic implant.
In other cases, the BCHD is not secured to the patient's head through magnetic means, but instead is secured or attached to the patient's head by mechanical means, such as by a headband, a strap and/or adhesive.
Whether or not magnetic coupling means are employed to secure a BCHD to a patient's head or skull, a perennial difficulty has been the degree and quality of acoustic coupling that is capable of being achieved between a BCHD and a patient's skull or head. Poor acoustic coupling of EM transducer signals through a patient's skin and/or hair can occur, which results in substandard transmission of such signals to the patient's skull.
What is needed is a BCHD or BCHD system that somehow provides improved acoustic coupling between the BCHD and a patient's head or skull.